Two Easy Ways to Start Earning Rewards!
Become a member today!
Members-only pricing and offers, personalized care notifications, Vital Care points back on every purchase and more!
Already a member? Sign in
Become a credit card member today!
Earn 2X Pals Rewards points at Petco
when you use Petco Pay!
APPLY NOW
Learn More About Petco Pay Benefits

My dog has a new lump behind his knee. Should I worry about cancer?

Updated on September 23rd, 2025

My dog developed a lump behind his right knee. It's about the size of a quarter and it wasn't there yesterday. He is a three year old neutered blue heeler mix who has had no previous health problems. How likely is it to be lymphoma?

3 Answers

Most Helpful Answer

Answered By Rebecca, DVM

Veterinarian

Published on August 22nd, 2017

I would recommend a vet visit. The vet can do a needle aspirate and take a look at the cells. While this may be a location for a lymph node it does not necessarily have to be lymphoma. Enlarged lymph nodes may be due to cancer, or inflammation or infection. Or it's possible it's not a lymph node and may be another type of mass or swelling. I recommend a vet visit to try to see what is swollen and why.

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Laura Johnson VMD
Veterinarian
Hi, thanks for using Petco Pet Education Center, formerly Petcoach!

If it is the only lymph node enlarged probably unlikely to be lymphoma. There are many causes for lumps under the skin: it could be a fatty deposit, skin infection, a cyst or a benign growth.

Since it is sudden it is not wrong to have your Vet take a look at the lump.

I wish you the best of luck!
1Pet Parents found this answer helpful
Answered By Dr. Elizabeth
Veterinarian
Published on August 30th, 2019
Any lymphnode that remains enlarged should progress onto another diagnostic. This next step could be either aspirating the lymphnode and sending the sample to a histopathologist in a lab or being a little more aggressive and get a biopsy and then sending that out. I recommend to choose one of these as the next step since the node has been enlarged for 3 months.
Regarding the other masses, pets can get many types of lumps and bumps. Most of these tumors will be benign but some will be malignant and you can't tell by looks. Here is a helpful link discussing the various types of skin masses in general:
https://www.petcoach.co/article/lumps-and-bumps-on-your-pet/

If any of these masses are changing, I would also recommend to collect a sample and send it out to a pathologist as well.

It's hard to know from the photo if that node looks enlarged or not, I generally need to compare the node to the other nodes via palpation. Have your vet double check the size of the node before aspiration. I hope this helps and please feel free to post any additional questions.
1Pet Parents found this answer helpful

Smart Picks for Smart Questions

Related Questions

What's this solid, unattached lump on my dog's leg near his knee?

I would have this lump on Jake examined by a vet. It could be a cyst, a benign tumor, or potentially a malignant tumor. Any suspicious lumps should be examined by the vet. The vet can perform a test called a fine needle aspirate on it. To do this, the vet sticks a small needle into the lump to get a sample of it's cells, and examines the cells on a slide under a microscope. It's usually painless to the animal, and relatively quick to perform. I'd recommend having Jake seen by a vet tomorrow to have the lump examined and diagnose so it can be treated as needed.

Updated on September 23rd, 2025

My dog has a lump on his leg. Is it serious? When should I see a vet?

That is a large, lobulated lump (no just one defined lump) in a location that would generally never have something like a swollen lymph nodes. I recommend making an appointment with your vet for a fine needle aspirate (where they aspirate cells from the mass and put them on a slide to be sent out for review) to determine if it is an abscess or a tumor/cancer of some sort. Best wishes for Diesel!

Updated on September 23rd, 2025

My dog has soft lumps behind his legs. When should I take him to the vet?

Depending on where the "knots" are, it is possible it is normal anatomy, however there could be something else going on. You may be feeling Cruz's lymph nodes if the "knots" you are feeling are behind the knees. Normally lymph nodes are small and not readily felt by owners, so it is very possible if you are able to feel them easily, that he needs to be checked out. Enlarged lymph nodes can be a nonspecific sign of infection or inflammation and should be checked out by your vet. Cruz is very young and so fatty lumps like lipomas, which are benign fatty tumors, are less likely. I would recommend having him checked out by your vet to see if these areas need to be investigated further or not.

Updated on September 23rd, 2025

Health & Wellness

My dog's knee lump tripled in size and turned dark purple. What now?

I'm concerned that this lump has tripled in size in such a short amount of time, and the color of it as well. Otis should go back to the vet for this to get it checked out, and I would take him into his vet this weekend or first thing Monday. The vet can perform a test called a fine needle aspirate on it. To do this, the vet sticks a small needle into the lump to get a sample of its cells, and examines the cells on a slide under a microscope. It's usually painless to the animal, and relatively quick to perform. Once the cause of the lump is diagnosed, the vet can discuss treatment options if needed. I hope this helps!

Updated on September 23rd, 2025

My 13-year-old dog has sore, growing lumps. Are they cancer?

With any new lump or lump that is changing, it is always best to have your veterinarian look at them and a fine needle aspirated can be done to obtain a sample of cells. If these cells look suspicious of a malignancy, then your vet can recommend surgery. From the photos that you have posted, my guess is that these may be benign, non-cancerous masses. These can still cause problems, though, by bleeding and getting infected. I would schedule Max for an exam at your earliest convenience so that you and your vet can weigh the pros and cons of surgery since he is a senior.

Updated on September 23rd, 2025

Health & Wellness

My dog has a lumpy, growing mass on his leg. What could it be?

Without a physical exam or diagnostics, it is difficult to determine if this is something to worry over. Ideally, a fine needle aspirate or biopsy should be done to collect samples for pathology. This may provide a diagnosis. X-rays of the limb may be recommended to rule out bony involvement. Since you state it is growing, it should be removed before it becomes too large. As it is, that is a difficult area to close after a mass removal.

Updated on September 23rd, 2025

Why does my dog have a hard, sudden, non-tender lump on his back leg?

Hello. A knot in the leg of a Chihuahua is unlikely and if it is behind the 'knee' then it is likely his lymph node. If it is larger than 1cmx1cm I would have it checked by a veterinarian. It may just be his normal lymph node however if it isn't sore or tender. Enlarged lymph nodes can be due to infection, or cancer. Due to his age it is much less likely to be cancer.

Updated on September 23rd, 2025

Have A Vet Question?

Book an appointment with the pros – our expert vets are here to help.

Share